Now that the river is back in the river, the weary and leery might come to thinking about the dirt of it.

Twice in a score of years the river has Tarred its cities. Twice in 20, the mild rivulet that is typically a 200-foot-wide driblet of muddy runoff has swollen to two miles Tar and wide. Whether a 100-year flood or a 1,000-year flood, this will leave its mark in the sediment record.

When the ancient Tigris and Euphrates Rivers flooded the Fertile Crescent of Mesopotamia 5,000 years ago at the dawn of words and wheels and wheat, the occasion was celebrated. Nutrient-rich silt and fresh irrigating water were suddenly in profuse supply. Livestock and plant stock might be destroyed, mud-brick homes might dissolve, but the new water and its catch of flora diaspora was beloved as a payday of fresh stocks and flocks. Now, here, in vivid relief, a residue coats our riverbanks much as it did the desert of ancient Mesopotamia.

The Tar leaves silt, but modern farming has made it unnecessary. We can feed our crops without deluging the lowlands. And the silt isn’t as nutritious as it used to be: spilled fuels, coal ash, automobile scrap and all manner of toss and trash wash in as waters rise, from nutrient-rich but pathogen-laden sewage and hog-pen wastes, to river park pet manure and discarded water bottles. In a million years, all of these will morph into a distinctive rock-layer remembrance of 2016.

Even when the river is not surging, every day we flood the sediments with modern clues for future anthropologists: the paper cup that merrily saltates across a parking lot gradually rolls downhill toward the river; the hot breath of our cars pastes soot on the roadway that ordinary rains then scrub out to sea; the butts and bits of cigarettes and snacks shred away to a contemporary compost. Wrinkled plastic grocery sacks hug the sweet gum trunks, mud-shaken beverage bottles stir to the bottom of Green Mill Run where reworked Miocene megalodon mouth parts munch them up, and glossy chip bags lie in wait at the river bed with mouths agape like inland crocs snap-tasting the tannins of the runoff. Another day, another detritus.

Sometimes floods are more permanent. Shokan, New York, population 1,183, is a rural Catskill Mountain hamlet known today for antique shops, fly fishing and its 100-mile proximity to New York City, but in 1955 it was the site of the new home designed and built by Mom and Dad, just the two of them, by hand and heart and hammer. In 1955, the area prided itself on its view, as Shokan winds along glacially deposited boulders and forests of pitch pine along the north shore of the Ashokan Reservoir at the base of Little Tonshi Mountain.

But it has not always been waterfront. Back at the turn of the 20th century, Shokan was a sleepy hollow deep in the V of the Tonshi valley. In 1907, New York City sought a supply of pristine drinking water, and the Catskill valley looked particularly moist and tasty. The city confiscated the heart of the hamlet (and 11 others) down in the valley, and in 1913-15 evacuated the residents and their belongings uphill by mule to a new Shokan-space and proceeded to flood the valley in a large public works project. Today, the ghosts of rerouted railroad ties and pre-diluvian tree stumps recast as sedimentary scum under the water’s surface by the dam.

Mesopotamia has left a trace of dirts and debris in a salty sandstone. A layer of Old Shokan still lingers in New York. And Hurricane Matthew will leave a Carolina legacy. As the coastal plain painstakingly piles up, mountain sediments falling in from the west overgird an old settlement of ooze from the last incursion of the Atlantic Ocean from the east, weaving dry over wet over dry.

In hundreds of thousands of years, the balled-up burger wrapper drooling cheesy orange offal into the wafting wind, catching on the floodwaters; the drained beer can, dancing a nay nay across the Town Common as the whipping waters rise; the roof shingle, torn from a bovine barn during a rousing gust, cartwheeling over the bank: all will slowly cast into fossil forms. Fish kills and landfills will press into dust. What will our future cousins learn of the year 2016 in eastern North Carolina from looking at our soil profile?

Joy Moses-Hall teaches physics and astronomy at Pitt Community College. She has a PhD in oceanography and is the author of the novel Wretched Refuge.